Polycarbonate polymers are known as being excellent molding materials since products made therefrom exhibit such properties as high impact strength, toughness, high transparency, wide temperature limits (high impact resistance below -60.degree. C. and a UL thermal endurance rating of 115.degree. C. with impact), good dimensional stability, good creep resistance, and the like.
Dimethylated aromatic polycarbonates are known as disclosed in U.S. Pat. No. 3,028,365. Tetramethylated aromatic polycarbonates are also known and their high heat distortion properties have been recognized as disclosed in U.S. Pat. No. 3,879,384. It would be desirable to add to this list of properties those of low water vapor transmission and low gas permeability to enable the aromatic polycarbonates to be used to form containers and film wraps for foods, beverages, cosmetics, and the like. In particular, food and beverage containers made from aromatic polycarbonates having these added barrier properties would be more economical as they would be capable of reuse and would thus also help reduce the impact of environmental waste occasioned by broken glass and discarded, non-reuseable containers.